In the next decade, defense spending on known medium- and large-size drones will be nearly $40 billion, increasing inventory by 35 percent. Ranging in size from a private aircraft to a commercial jet, nearly 800 of these bigger drones are operating around the world, observing, collecting data and in some cases attacking the enemy. The military also has thousands of mini-drones used for battlefield surveillance. Since 2001, the U.S. government is estimated to have killed more than 2,000 militants and civilians in drone attacks. Read related article.